Epicyclic trains

ABSTRACT

1,140,115. Toothed gearing. DAVID BROWN GEAR INDUSTRIES Ltd. 8 Aug., 1967 [12 Aug., 1966], No. 36165/66. Heading F2Q. An epicyclic gear train comprises an element supported by an hydraulic mechanism of variable torsional rigidity. As shown, an annulus 10 is supported circumferentially by three piston and cylinder assemblies 12, one end of each cylinder being connected hydraulically with a master cylinder 15, and the other end of each cylinder being connected hydraulically with a sump 19. The master cylinder 15, sump 19 and an accumulator 18 all communicate hydraulically with a bore 20 formed in a valve body 21 containing a spool 22 adapted, when moved from a neutral position, to cause the master cylinder to communicate hydraulically with either the accumulator 18 or the sump 19. The spool 22 is connected to annulus 10 by a rod 23. A pump 24, driven from a sun gear 8, is connected hydraulically to sump 19 and accumulator 18. The master cylinder 15 contains a piston 16 acted upon by a spring 17, so that effectively the annulus 10 is connected to its casing by the spring 17, and hence its torsional rigidity increases as its angular displacement increases.

Aug. 12, 1969 N. c. SIMMONS 3,460,405

EPICYCLIC TRAINS Filed July 17. 1967 INVENTOR NoRmAN cYRIu SIMMONS BY \Mmq-QML ATTORNEYS United States Patent 3,460,405 EPICYCLIC TRAINS Norman C. Simmons, Lockwood, England, assignor to David Brown Gear Industries Limited Filed July 17, 1967, Ser. No. 653,814 Claims priority, application Great Britain, Aug. 12, 1966, 36,165 66 Int. Cl. F16h 1/28, 57/00 US. Cl. 74-801 6 Claims ABSTRACT OF THE DISCLOSURE An epicyclic gear train has an annulus torsionally supported by three piston-and-cylinder assemblies. The supply ot fluid to said assemblies is controlled by a valve which is operated by angular displacement of the annulus to allow fluid to flow to a master-cylinder and then to the assemblies to control the movement of the annulus. The master-cylinder incorporates a spring-loaded piston which allows limited angular displacement of the annulus with low torsional resistance thus reducing vibration.

Background of invention The invention relates to epicyclic gear trains. Previously members of epicyclic gear trains have been resiliently mounted but tend to suffer from the disadvantage of transmitting vibration through such trains.

Summary of invention The object of the invention is to minimize the transmission of vibration through epicyclic gear trains.

According to the invention, an epicyclic gear train com prises an element supported by a hydraulic mechanism of variable torsional rigidity.

Brief description of drawings The accompanying drawing, which is by way of example only, is a diagrammatic representation of a preferred form of the invention.

Description of prefered embodiment Referring now to the accompanying drawing, an epicyclic gear train comprises a sun 8, planets 9, and an annulus or ring gear 10. The annulus 10 is supported relative to a co-axial case 11 by three symmetrically-disposed piston-and-cylinder assemblies 12, each pivotally connected between a radially-extending lug 13 formed integrally with the annulus 10 and a radially-extending lug 14 formed integrally with the case 11. Congruent ends of the piston-and-cylinder assemblies 12 all communicate hydraulically with a master-cylinder 15 rigidly secured to the case 11 and adapted to be closed at one end by a piston 16 movable against the action of a helical compression spring 17. The master-cylinder 15, an accumulator 18, and a sump 19, all communicate hydraulically with a bore 20 formed in a valve body 21 rigidly secured to the case 11. The bore 20 contains a spool 22 adapted, when 3,460,405 Patented Aug. 12, 1969 ice moved from a neutral position, to cause the master-cylinder 15 to communicate hydraulically with either the accumulator 18 or the sump 19. A rod 23 pivotally connected between the spool 22 and one of the lugs 13 controls the movements of said spool. he accumulator 18 and the sump 19 both communicate hydraulically with a pump 24 drivably conected to the sun 8 of the epicyclic gear train, and those ends of the piston-and-cylinder assemblies 12 not communicating hydraulically with the master-cylinder 15 all communicate hydraulically with the sump 19 via a restricted orifice 25.

In operation, the annulus 10 is centred by the planets 9 and is subjected to a torque, acting in the direction of the arrow A, Which is counteracted by movement of the spool 22 causing the pressure of fluid in the piston-andcylinder assemblies 12 and the master-cylinder 15 to vary appropriately. Consequently, when the torque to which the annulus 10 is subjected becomes substantially constant, i.e. when the epicyclic gear train achieves steady running conditions, the spool 22 assumes its neutral position shown in the drawing. Then, as the force exerted on the piston 16 by the spring 17 is proportional to the pressure of fluid in the master-cylinder 15, the annulus 10 is eiiectively connected to the case 11 by the spring 17 which is arranged to have a very low rate to minimize the transmission of vibration. Those ends of the pistonand-cylinder assemblies 12 communicating hydraulically with the sump 19 via the restricted orifice 25 act to damp down oscillations of the annulus 10.

In effect, the hydraulic mechanism, is of very low stiffness against a small displacement of the annulus 10 but is infinitely stifi to a larger displacement thereof.

The hydraulic mechanism as hereinbefore described can be adapted to support any element of an epicyclic gear train and the response thereof to the initial displacement of the supported element can be accelerated by driving the pump 24 independently of the epicyclic gear train.

I claim:

1. The combination of an epicyclic gear train at least one element of which is movably supported by a hydraulic mechanism comprising at least three piston-andcylinder assemblies operatively connected between said element and a relatively fixed member, a master-cylinder of variable volume having a piston urged by resilient means towards the minimum volume position, and means for supplying fluid to said master-cylinder; characterized in that one end of each cylinder of said hydraulic mechanism is hydraulically connected to said master-cylinder and the other end of each said cylinder is hydraulically conected through an orifice to a sump.

2. The combination according to claim 1, further characterized in that said means for supplying fluid to the master-cylinder includes a valve hydraulically connecting said master-cylinder selectively to a source of fluid at a predetermined pressure and the sump.

3. The combination according to claim 2, further characterized in that the valve comprises a spool connected to said element.

4. The combination according to claim 3, further characterized in that the spool and associated valve passages are so dimensioned that the valve is inoperative until after a predetermined angular displacement of said element relative to the fixed member.

5. The combination according to claim 1, further characterized in that said piston-and-cylinder assemblies are pivotally conected to radially extending projections on said element and the fixed member.

6. The combination defined in claim 1, wherein said element is a ring gear and said piston-and-cylinder assemblics are cir-cumferentially spaced around said ring gear and pivotally conected at opposite ends to said ring gear and fixed member.

References Cited UNITED STATES PATENTS DONLEY J. STOCKING, Primary Examiner THOMAS C. PERRY, Assistant Examiner US. Cl. X.R. 

